By the end of the 20th century, at least two trends had become apparent in flood hazards and flood-hazard mitigation. The first of these was an increase in flood damages in most countries. In the United States, flood hazards at the end of the 20th century were emphasized by the 1993 flood on the upper Mississippi River, which caused 38 deaths and 12 to 16 billion dollars in damage (Galloway, 1994). This flood was the most prominent in a series of floods; more than 80% of presidentially declared disasters in the closing decades of the century resulted from floods (National Mitigation Strategy, 1995). Van der Vink et al. (1998) attributed the increase in flood damages to changes in population and national wealth density, instead of to an increase in flood magnitude and/or frequency. Although improvements in flood forecasting, warning systems, and building codes greatly reduced the number of fatalities resulting from floods in the United States during the 1990s, the percentage of national wealth spent on homeowners' and property/casualty insurance remained approximately constant with respect to gross national product (Council of Economic Advisors, 1994; U.S. Census Bureau, 1997; Van der Vink et al., 1998). This increase in flood damages has also occurred in other countries, although in developing nations both deaths and damage to structures during floods have increased.